Hi.

First of all....24? Too young?? hmf! LOL!! I wish sometimes that I was one of those 24 year olds. Only sometimes.

Does she have any other friends??
I've had my fair share of single parenting. DH has gone away for work alot. Usually I am more relaxed when he's not here. More because I can do what I want with the kids with out having to worry about him & what he might need the car for etc. And I get better sleep when I've got the bed & blankets to myself!
If it is longer than the expected time it starts to get a bit much. I do have 3 kids though. When I was pg with DD2 he was away for a month & my main problem was lonliness. & boredom.
These days it's lonliness & noone here every night to give me a break. But then I don't have anyone to take my kids over night close by either.
Does she go to play group? Does she do anything on the nights her IL's have her DD? Maybe she needs something to do to take up some time & get her mind off things. Maybe the two of you could take your kids & go for coffee every few days. Just so she gets out of the house. I know coffee with kids that age isn't the easiest thing, but it might be good. Or just to the park.

You are a really good friend. She's lucky to have you. Ask her about it. Ask if she thinks she's coping. Maybe she just needs to talk to someone.